1. Field of the Invention
The present invention relates to a weather strip for a motor vehicle, which is formed by extrusion and used to provide a seal between a door member such as a vehicle door, a trunk lid, etc., and a periphery around an opening in a vehicle body.
2. Description of Related Art
As shown in FIG. 1, a weather strip 10 for a motor vehicle has a trim portion 12 as a base portion for attachment to a periphery around an opening in a vehicle body, and a tubular sealing portion 14 for contacting a door member and providing a seal between the vehicle body and the door member. The trim portion 12 has an outer side wall 16, an inner side wall 18 and a bottom wall 20 and has a generally U-shaped cross-section, and in order to enlarge the gripping force of the trim portion 12, an insert 22 produced by forming slits in a band-shaped metallic plate, and rolling or punching the same is embedded in the trim portion 12 (see Publication of Japanese Utility model application No. 2005-231222, for example). A first outer holding lip 24 and a second outer holding lip 26 are formed in an interior surface of the outer side wall 16, and a first inner holding lip 28 and a second inner holding lip 30 are formed in an interior surface of the inner side wall 18.
As shown in FIG. 2, this insert 22 is composed of a large number of rectangular insert pieces 32, each extending in a widthwise direction of the insert 22, and the insert pieces 32 are joined to each other in their both ends with joining parts extending in a longitudinal direction to define a ladder-like configuration. The joining parts are formed by rolling the both ends of the insert pieces 32, thereby defining first joining parts 34, each having a smaller width so as to be readily breakable, and second joining parts 36, each having a larger width so as to be difficult to break. The first joining parts 34 and adjacent insert pieces 32 define first slits 38, whereas the second joining parts 36 and adjacent insert pieces 32 define second slits 41.
Upon producing a long product, namely upon feeding the insert 22 to an extruder and forming a covering layer of a rubber-like elastic body therearound, the joining parts of the insert 22 remain joined for facilitating taking up of the long product. But, when the long product is used to be attached along corners of the flange, etc., the joining parts are separated for enhancing the flexibility of the trim portion 12.
Therefore, after extruding the long product, the first joining parts 34 of the insert 22 are broken and separated, and consequently, there exist in the trim portion 12, a plurality of pairs of insert pieces 32, each being joined on an upper side and a lower side thereof with the second joining parts 36, thereby defining the second slits 41.
Recently, in order to protect the global environment, the reduction of the weight of motor vehicles has been demanded, and the reduction of the weight of the weather strip 10 has been also demanded. In order to respond to this demand, the thickness of the side walls of the trim portion 12 has been tried to be reduced. And in order to reduce the weight of the insert 22, the thickness of the insert 22 has been considered to decrease, thereby rolling the joining parts greatly and increasing the length of rolled portions.
When a flange 40 formed in a door or along the periphery of the door opening portion is inserted in an interior of the trim portion 12, the first outer holding lip 24, the second outer holding lip 26, the first inner holding lip 28 and the second inner holding lip 30 respectively hold the flange 40, thereby attaching the weather strip 10 to the vehicle body. Especially, the first outer holding lip 24 and the second outer holding lip 28 provided on the side of the bottom wall 20 exhibit great holding forces against the flange 40 so as to be important for holding the flange 40.
The covering layer of the rubber-like elastic body, which composes the trim portion 12, is formed on both sides of the insert 22 of the trim portion 12. The covering layer of the rubber-like elastic body formed on both sides of the insert 22 is integrally joined via the first slits 38 and the second slits 41, whereby the covering layer is secured to the insert 22.
However, the covering layer of the rubber-like elastic body on both sides of the first joining parts 34 and the second joining parts 36 of the insert 22 is not integrally joined but separated. And where the thickness of the covering layer is decreased for reducing the weight of the weather strip, the longitudinal length of the first joining parts 34 and that of the second joining parts 36 after rolled becomes great.
Therefore, as shown in FIG. 1 and FIG. 3, where a base 42 of the first outer holding lip 24 and/or a base 44 of the second outer holding lip 28 face the first joining parts 34 and the second joining parts 36, the base 42 of the first outer holding lip 24 and/or the base 44 of the second outer holding lip 28 may separate from the insert 22, whereby the holding force of the first outer holding lip 24 and/or the second outer holding lip 28 against the flange 40 may decrease so that the extraction load of the trim portion 12 from the flange 40 may decrease.
And, as shown in FIG. 4, there is a weather strip 46 having a trim portion 48 and a tubular sealing portion 50, in which an insert 52 is not separated after extrusion (see Publication of Japanese Patent application No. 2008-265068 and Publication of Japanese Patent application No. 2002-200944, for example). In this weather strip 46, the trim portion 48 includes an outer side wall 54, an inner side wall 56 and a bottom wall 58 with a generally U-shaped cross-section, and an outer holding lip 60 and an inner holding lip 62 are formed in interior surfaces of the outer side wall 54 and the inner side wall 56. In order to improve the flexibility of the weather strip 46, joining parts 64 of the insert 52 are located away from parts facing a base 66 of the outer holding lip 60 and a base 68 of the inner holding lip 62 towards the bottom wall 58.
In order to form this weather strip 46, the insert 52 with a plate-shaped configuration is extruded with a covering layer, and subjected to the bending work into a generally U-shaped cross-section. At this time, the joining parts 64 of the insert 52 may come close to bent parts between the bottom wall 58 and the outer side wall 54 and the inner side wall 56, whereby the insert 52 may be bent in the vicinity of the joining parts 64 and consequently, the trim portion 48 may be deformed.
In addition, the outer side wall 54 and the inner side wall 56 peel off and swell inwardly in the vicinity of the joining parts 64, and consequently, the insertion of the flange 40 may become insufficient, or upon attaching a sealer and a waterproof sponge to the trim portion 48, the attaching positions thereof may vary to degrade the sealing properties against a tip end of the flange 40.
Furthermore, the length from the joining parts 64 to ends of rectangular pieces 70 of the insert 52 becomes great to increase an extrusion resistance upon extruding a covering layer of the trim portion 48.